Final answer:
The question asks for the calculation of the radiation dose in rem received by a tumor from y rays during cancer treatment, using the provided exposure data and the energy per decay. It also inquires about whether this dose adheres to standard therapeutic doses
Step-by-step explanation:
The student's question pertains to a cancer patient receiving y rays as part of a therapeutic procedure and the calculation of the dose in rem to the tumor. The exposure scenario describes a 5000-Ci Cobalt-60 (60Co) transillumination unit, where only 1% of the emitted rays strike the patient, and 20% of these rays are absorbed by a tumor weighing 1.5 kg. The given average energy per decay of the y rays is 1.25 MeV. To calculate the dose in rem, absorbed energy in rads must be multiplied by the relative biological effectiveness (RBE), which will be provided in relevant tables or factors. The question also contemplates whether this administered dose is within the therapeutic range typically employed in medical treatments.
Diagnostic and therapeutic doses in medicine vary, depending on the procedure and tissue type, and they are carefully justified by weighing the risk versus benefit. For instance, the doses range from 0.1 mSv for a chest x-ray to 0.75 Sv for a thyroid scan using 131I, in cases where longer exposure is necessary due to a longer half-life. Thus, the question also implies an analysis of acceptable medical radiation dose levels.